/**
 * VerdictDigest Tests
 * Sprint: SPRINT_9100_0002_0002 (Per-Node VerdictDigest)
 * Tasks: VDIGEST-9100-016 through VDIGEST-9100-021
 */

using System.Text.Json;
using Xunit;

using StellaOps.TestKit;
namespace StellaOps.Resolver.Tests;

public class VerdictDigestTests
{
    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDigest_IsDeterministic()
    {
        // VDIGEST-9100-016: Same verdict → same digest
        var nodeId = NodeId.From("package", "test");
        var evidence = JsonDocument.Parse("{\"reason\": \"test\"}").RootElement;

        var verdict1 = Verdict.Create(nodeId, VerdictStatus.Pass, evidence, "Test reason", 0);
        var verdict2 = Verdict.Create(nodeId, VerdictStatus.Pass, evidence, "Test reason", 0);

        Assert.Equal(verdict1.VerdictDigest, verdict2.VerdictDigest);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDigest_ChangesWhenStatusChanges()
    {
        // VDIGEST-9100-017: Digest changes with status
        var nodeId = NodeId.From("package", "test");
        var evidence = JsonDocument.Parse("{\"reason\": \"test\"}").RootElement;

        var passVerdict = Verdict.Create(nodeId, VerdictStatus.Pass, evidence);
        var failVerdict = Verdict.Create(nodeId, VerdictStatus.Fail, evidence);

        Assert.NotEqual(passVerdict.VerdictDigest, failVerdict.VerdictDigest);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDigest_ChangesWhenEvidenceChanges()
    {
        // VDIGEST-9100-018: Digest changes with evidence
        var nodeId = NodeId.From("package", "test");
        var evidence1 = JsonDocument.Parse("{\"reason\": \"reason1\"}").RootElement;
        var evidence2 = JsonDocument.Parse("{\"reason\": \"reason2\"}").RootElement;

        var verdict1 = Verdict.Create(nodeId, VerdictStatus.Pass, evidence1);
        var verdict2 = Verdict.Create(nodeId, VerdictStatus.Pass, evidence2);

        Assert.NotEqual(verdict1.VerdictDigest, verdict2.VerdictDigest);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDelta_CorrectlyIdentifiesChangedVerdicts()
    {
        // VDIGEST-9100-019: Delta detection identifies changed verdicts
        var nodeId1 = NodeId.From("package", "a");
        var nodeId2 = NodeId.From("package", "b");

        var oldVerdicts = new[]
        {
            Verdict.Create(nodeId1, VerdictStatus.Pass, null),
            Verdict.Create(nodeId2, VerdictStatus.Pass, null)
        };

        var newVerdicts = new[]
        {
            Verdict.Create(nodeId1, VerdictStatus.Pass, null),
            Verdict.Create(nodeId2, VerdictStatus.Fail, null) // Changed
        };

        var oldResult = new ResolutionResult
        {
            TraversalSequence = [nodeId1, nodeId2],
            Verdicts = [.. oldVerdicts],
            GraphDigest = "abc",
            PolicyDigest = "def",
            FinalDigest = "old"
        };

        var newResult = new ResolutionResult
        {
            TraversalSequence = [nodeId1, nodeId2],
            Verdicts = [.. newVerdicts],
            GraphDigest = "abc",
            PolicyDigest = "def",
            FinalDigest = "new"
        };

        var detector = new DefaultVerdictDeltaDetector();
        var delta = detector.Detect(oldResult, newResult);

        Assert.Single(delta.ChangedVerdicts);
        Assert.Equal(nodeId2, delta.ChangedVerdicts[0].Old.Node);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDelta_HandlesAddedRemovedNodes()
    {
        // VDIGEST-9100-020: Delta handles added/removed nodes
        var nodeId1 = NodeId.From("package", "a");
        var nodeId2 = NodeId.From("package", "b");
        var nodeId3 = NodeId.From("package", "c");

        var oldResult = new ResolutionResult
        {
            TraversalSequence = [nodeId1, nodeId2],
            Verdicts = [
                Verdict.Create(nodeId1, VerdictStatus.Pass, null),
                Verdict.Create(nodeId2, VerdictStatus.Pass, null)
            ],
            GraphDigest = "abc",
            PolicyDigest = "def",
            FinalDigest = "old"
        };

        var newResult = new ResolutionResult
        {
            TraversalSequence = [nodeId1, nodeId3],
            Verdicts = [
                Verdict.Create(nodeId1, VerdictStatus.Pass, null),
                Verdict.Create(nodeId3, VerdictStatus.Pass, null)
            ],
            GraphDigest = "abc",
            PolicyDigest = "def",
            FinalDigest = "new"
        };

        var detector = new DefaultVerdictDeltaDetector();
        var delta = detector.Detect(oldResult, newResult);

        Assert.Single(delta.AddedVerdicts);
        Assert.Single(delta.RemovedVerdicts);
        Assert.Equal(nodeId3, delta.AddedVerdicts[0].Node);
        Assert.Equal(nodeId2, delta.RemovedVerdicts[0].Node);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void VerdictDigest_ExcludesItselfFromComputation()
    {
        // VDIGEST-9100-021: Property test - no recursion
        var nodeId = NodeId.From("package", "test");

        // Create two verdicts with the same input data
        var verdict1 = Verdict.Create(nodeId, VerdictStatus.Pass, null, "reason", 0);
        var verdict2 = Verdict.Create(nodeId, VerdictStatus.Pass, null, "reason", 0);

        // Digests should be identical and stable (not including themselves)
        Assert.Equal(verdict1.VerdictDigest, verdict2.VerdictDigest);
        Assert.Equal(64, verdict1.VerdictDigest.Length); // Valid SHA256
    }
}